Display panel, method of manufacturing the same, and frit composition used in the display panel

ABSTRACT

Provided are display panel, method of manufacturing the same, and frit composition used in the display panel. A display panel comprising: a first substrate, a second substrate facing the first substrate and a frit bonding the first substrate and the second substrate together, wherein the frit has an optical density of more than about 0.0683 μm for laser light of any one wavelength in a wavelength range of about 760 to about 860 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application which claims priority under35 U.S.C §120 from U.S. patent application Ser. No. 13/341,791, filedDec. 30, 2011, which claims priority to and the benefit of Korean PatentApplication No. 10-2011-0059177 filed on Jun. 17, 2011 in the KoreanIntellectual Property Office, the disclosure of each of which isincorporated herein by reference.

BACKGROUND

1. Field

The present embodiments relate to a display panel including a glasspackage sealed with a frit, a method of manufacturing the display panel,and a frit composition used in the display panel.

2. Description of the Related Technology

An organic light-emitting diode (OLED) display is a self-luminousdisplay and includes an organic material between two electrodes. TheOLED display emits light when injected electrons and holes recombine inthe organic material.

Electrodes and an organic layer within an OLED display are readilydamaged by interaction with oxygen and moisture that get into the OLEDdisplay. Thus, a frit is interposed between glass substrates to sealthem and protect internal devices against oxygen and moisture.

To improve the sealing capability of a frit, an effective seal width ofthe frit should be increased. The effective seal width of the fritdepends on how effectively the frit is heated and melted when upper andlower substrates are bonded together.

SUMMARY

Aspects of the present embodiments provide a display panel with asuperior sealing capability.

Aspects of the present embodiments also provide a method ofmanufacturing a display panel with a superior sealing capability.

Aspects of the present embodiments also provide a frit composition witha superior sealing capability.

However, aspects of the present embodiments are not restricted to theone set forth herein. The above and other aspects of the presentembodiments will become more apparent to one of ordinary skill in theart to which the present embodiments pertain by referencing the detaileddescription of the present embodiments given below.

According to an aspect of the present embodiments, there is provided

A display panel comprising:

a first substrate, a second substrate facing the first substrate and afrit bonding the first substrate and the second substrate together,wherein the frit has an optical density of more than about 0.0683 μm forlaser light of any one wavelength in a wavelength range of about 760 toabout 860 nm.

According to another aspect of the present embodiments, there isprovided

A method of manufacturing a display panel, the method comprising:

preparing a first substrate and a second substrate, coating a fritcomposition, which has an optical density of more than about 0.0683 μmfor laser light of a wavelength of 810 nm, on the second substrate,stacking the first substrate on the frit composition and sintering thefrit composition by irradiating the laser light of the wavelength of 810nm to the frit composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present embodiments willbecome more apparent by describing in detail example embodiments thereofwith reference to the attached drawings, in which:

FIG. 1 is a schematic layout view of a display panel according to anexample embodiment;

FIG. 2 is a cross-sectional view of the display panel shown in FIG. 1;

FIG. 3A is a scanning electron microscope (SEM) photograph of a frit;

FIG. 3B is a schematic diagram illustrating a seal width of the frit ofFIG. 3A;

FIG. 4 is a flowchart illustrating a method of manufacturing a displaypanel according to an example embodiment;

FIG. 5 is a graph illustrating the relationship between the content of avanadium compound in a vanadium-based frit and the optical density ofthe vanadium-based frit;

FIG. 6 is a diagram illustrating a seal width of each sample of FIG. 5;

FIG. 7 is a graph illustrating the relationship between the type of apigment contained in a bismuth-based frit and the optical density of thebismuth-based frit;

FIG. 8 is a diagram illustrating a seal width of each sample of FIG. 7;

FIG. 9 is a graph illustrating the relationship between the content ofMn in a frit having a Mn-containing pigment and the optical density ofthe frit;

FIG. 10 is a diagram illustrating an effective seal width of each sampleof FIG. 9; and

FIG. 11 is a graph illustrating an optical density range of abismuth-based frit which is required for laser sealing.

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafterwith reference to the accompanying drawings, in which preferredembodiments are shown. The present embodiments may, however, be embodiedin different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the embodiments to those skilled in the art. Thesame reference numbers indicate the same components throughout thespecification. In the attached figures, the thickness of layers andregions is exaggerated for clarity.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which these embodiments belong. It is noted that the use ofany and all examples, or example terms provided herein is intendedmerely to better illuminate the embodiments and is not a limitation onthe scope of the embodiments unless otherwise specified. Further, unlessdefined otherwise, all terms defined in generally used dictionaries maynot be overly interpreted.

FIG. 1 is a schematic layout view of a display panel 100 according to anexample embodiment. FIG. 2 is a cross-sectional view of the displaypanel 100 shown in FIG. 1.

Referring to FIGS. 1 and 2, the display panel 100 includes a firstsubstrate 400, a second substrate 300, and a frit 200 interposed betweenthe first substrate 400 and the second substrate 300.

The first substrate 400 may be made of a glass material such asborosilicate glass, soda-lime glass, or a mixture of the same. However,the present embodiments are not limited thereto.

The first substrate 400 may receive thermal stress from a heating member(such as a laser) used in the process of attaching the frit 200 to thefirst substrate 400. Thus, the first substrate 400 may be made of amaterial that hardly absorbs a wavelength range corresponding to thermalenergy generated from the heating member.

A plurality of micro devices for light emission may be formed on thefirst substrate 400. For example, a plurality of light-emitting unitsmay be formed on the first substrate 400. Here, the light-emitting unitsmay be organic light-emitting diodes (OLEDs), and each of the OLEDs mayhave a stacked structure of a cathode electrode which provideselectrons, an electron injecting layer which transports the electronsprovided by the cathode electrode, an organic emitting layer which emitslight when transported electrons and holes react with each other toexcite organic molecules, a hole injecting layer which transports holesprovided by an anode electrode, and the anode electrode which providesthe holes.

A plurality of thin-film transistors (TFTs) may further be formed on thefirst substrate 400. When a light-emitting unit includes an OLED, a TFTmay be connected to at least one of the cathode electrode and the anodeelectrode of the OLED to control the provision of current to theconnected one or ones of the cathode electrode and the anode electrode.

The second substrate 300 faces the first substrate 400 and covers thelight-emitting units located on the first substrate 400. Like the firstsubstrate 400, the second substrate 300 may be made of a glass materialsuch as borosilicate glass, soda-lime glass, or a mixture of the same.In addition, like the first substrate 400, the second substrate 300 maybe made of a material that hardly absorbs the wavelength rangecorresponding to the thermal energy generated from the heating member.

The frit 200 is interposed between the first substrate 400 and thesecond substrate 300 and provides a sealed space between the firstsubstrate 400 and the second substrate 300. To provide a sufficientlylarge sealed space in a central region of the first and secondsubstrates 400 and 300, the frit 200 may be formed in peripheral regionsthereof. The frit 200 may be formed by sintering a frit composition.

To fully seal a display region from the outside environment with thefrit 200, a seal width of the frit 200 should be large enough to becomean effective seal width. Here, the seal width may denote a width whichenables the frit 200 to connect the frit substrate 400 and the secondsubstrate 300 after being melted by thermal energy it absorbs and thensintered and which enables the frit 200 to block outside air andmoisture. The seal width will now be described in greater detail withreference to FIGS. 3A and 3B.

FIG. 3A is a scanning electron microscope (SEM) photograph of the frit200. FIG. 3B is a schematic diagram illustrating the seal width of thefrit 200 of FIG. 3A. Referring to FIGS. 3A and 3B, a width of the frit200 attached onto the first and second substrates 400 and 300 is notalways equal to a width D of the entire frit 200. As shown in FIG. 3B, awidth of the frit 200 in a region in which the frit 200 is attached ontothe second substrate 300 to contact the second substrate 300 is equal tothe maximum width D of the frit 200. However, a width d of the frit 200in a region in which the frit 200 is attached onto the first substrate400 to contact the first substrate 400 may be smaller than the maximumwidth D of the frit 200 due to empty spaces 500 and 550 at edges of thefrit 200. In this case, a width that contributes to sealing the displaypanel 100 from outside air and moisture is the width d of the frit 200attached onto the first substrate 400. Accordingly, the seal width isdetermined to be the width d of the frit 200 actually attached onto thefirst substrate 400, excluding the edges of the frit 200 (e.g., theempty spaces 500 and 550) which are not connected to the first substrate400.

Unlike in the example illustrated in FIGS. 3A and 3B, the width of thefrit 200 attached onto the first substrate 400 may also be smaller thanthe width D of the entire frit 200. In this case, a smaller one of thewidth of the frit 200 attached onto the first substrate 400 and thewidth of the frit 200 attached onto the second substrate 300 isdetermined to the seal width.

The effective seal width may denote a seal width large enough to enablethe frit 200 to connect the first substrate 400 and the second substrate300 and block outside air and moisture. For example, when a ratio of aseal width to the maximum width D of the frit 200 is about 0.7 orhigher, it can be determined that the effective seal width has beenformed. Specifically, when the maximum width D of the frit 200 is 600μm, if a seal width that enables the frit 200 to block outside air andmoisture is 420 μm or more, it can be determined that the effective sealwidth has been formed. Likewise, when the maximum width D of the frit200 is 1200 μm, a seal width of 840 μm or more may be determined to bethe effective seal width.

The seal width of the frit 200 may be symmetrical with respect to acenter line of the frit 200. However, the seal width may also be invarious forms.

After materials that form the frit 200 are heated using the heatingmember, some of the materials that form the frit 200 may not be properlysintered into the frit 200. The materials that are not properly sintereddo not contribute to the sealing of the display panel 100. A seal widthformed large enough to exceed the effective seal width through a smoothsintering process is closely related to the degree of sealing of thedisplay panel 100.

To increase the effective seal width of the frit 200, it is desirablefor the frit 200 to fully absorb thermal energy from the heating member.For example, the use of a frit having a high optical density, whichindicates the degree of absorption of radiant energy, is advantageous tothe sealing of the display panel 100. The heating member may be laserlight of any one wavelength in a wavelength range of 760 to 860 nm.

The optical density may also be referred to as an extinction coefficientand may be measured in [/μm]. Absorbance and extinction coefficient maysatisfy the following equations.

Absorbance=A=log(1/t)=log(1/(It/Io))=−log(It/100)=εCL,

Extinction coefficient=A/L=εC,

where t=It/Io represents the intensity of transmitted light/theintensity of incident light (the incident light: 100%, the transmittedlight: measured transmittance (%)), ε represents a proportionalconstant, C represents the concentration of a sample (it is assumed thatthe concentration of the sample is constant), and L represents thelength (thickness) of the sample.

When the transmittance of a sample for laser light of any one wavelengthin a wavelength range of about 760 to about 860 nm, for example, laserlight of 810 nm is 20%, if the sample has a thickness of 5 μm, A(absorbance)=−log(20/100)=0.69897, and A/L=εC (extinctioncoefficient)=0.69897/5 μm=0.139794/μm.

Hereinafter, an optical density range that ensures superior sealingperformance of the frit 200 and methods of achieving optical densitiesin this optical density range will be described.

In a frit-sintering process using a laser, an optical density of a fritdetermines a seal width of the frit. If a minimum optical density forforming an effective seal width can be identified, the time required toselect materials that form the frit can be reduced based on theidentification result, which, in turn, reduces the entire frit process.An optical density that allows a frit to have an effective seal widthafter being irradiated with laser light of 810 nm varies according tocharacteristics of mother glass or other components of the frit.Components of a frit and a minimum optical density of the frit willhereinafter be described in detail.

A frit may include mother glass and ceramic filler. In some embodiments,the mother glass may be vanadium-based mother glass including aplurality of compounds. For example, the vanadium-based mother glass mayinclude about 40 to about 50% by mole of V₂O₅, which is a vanadium-basedcompound, based on the total content of the frit and may further includeTeO₂, BaO, and ZnO.

The ceramic filler is distributed within the mother glass to maintainthe shape of the sintered frit. In addition, the ceramic filler controlsa coefficient of thermal expansion (CTE) of the frit to maintain themechanical strength of the frit. More specifically, the ceramic fillermay be made of a material having a relatively lower CTE than the motherglass. Therefore, even when the mother glass has a relatively high CTE,since the CTE of the mother glass is offset by the CTE of the ceramicfiller, the CTE of the frit can be maintained low. A lower CTE increasesmechanical strength against heat. Therefore, the ceramic fillercontributes to an increase in the mechanical strength of the frit. Whenthe vanadium-based mother glass is used as the mother glass, the ceramicfiller mixed with the vanadium-based mother glass may be, e.g.,Zr₂(WO₄)(PO₄)₂.

As verified through experimental examples which will be described later,a vanadium-based frit should have an optical density of more than about0.0683/μm in order to have an effective seal width after beingirradiated with laser light of any one wavelength in a wavelength rangeof about 760 to about 860 nm, for example, laser light of 810 nm. Anupper limit of the optical density of the frit may be 0.2/μm. An opticaldensity of 0.2/μm or less can prevent sintering defects at each fritheight due to a reduction in the transmittance of laser light.

The content of a vanadium-based component in the vanadium-based frit maychange the optical density of the frit. Specifically, the vanadium-basedcomponent may be, e.g., V₂O₅. When the content of V₂O₅ in thevanadium-based frit is about 40 to about 50% by mole, a high opticaldensity can be obtained. In some other embodiments, the vanadium-basedfrit may further include V₂O₄. In this case, the sum of the content ofV₂O₄ and the content of V₂O₅ may be about 40 to about 50% by mole. SinceV₂O₄ is more brownish in color than V₂O₅, a greater content of V₂O₄ maylead to a higher absorption rate of thermal energy, thereby increasingthe optical density of the vanadium-based frit.

In order to increase the content of V₂O₄ in the frit, a frit compositionmay be plasticized in a N₂ atmosphere. Specifically, the vanadium-basedmother glass that contains V₂O₅ is yellowish due to a vanadium componentof a pentavalent ion. If a vanadium-based compound has a chemicalreaction in a N₂ environment, VO₂ is contained in the resultantcompound. The chemical reaction formula of the vanadium-based motherglass in the N₂ environment is as follows.

V₂O₅+C→2VO₂+CO₂↑

Therefore, the resultant compound includes a vanadium component of atetravalent ion, and vanadium of the tetravalent ion is brownish incolor. This corresponds to a condition that increases the frit'sabsorption rate of thermal energy, thus increasing the optical densityof the frit.

During the process of plasticizing the frit, a flow rate of oxygen in aworkspace should be maintained at a predetermined rate or higher inorder to induce a desired chemical reaction. Therefore, the flow rate ofN₂ in the workspace for the plasticizing process needs to be adjusted inview of the flow rate of oxygen in the workspace. For example, the flowrate of N₂ in the workspace for the plasticizing process may be 30 to40% by volume.

In some other embodiments, the mother glass of the frit may bebismuth-based mother glass including a plurality of compounds. Thebismuth-based glass may include 30 to 45% by mole of Bi₂O₃ based on thetotal content of the frit and may further include ZnO, B₂O₃, BaO, Al₂O₃,SiO₂, and MgO. Here, the ceramic filler that can be mixed with thebismuth-based mother glass may be, e.g., Mg₂(Al₄O₃(SiO₃)₅)).

As verified through the experimental examples which will be describedlater, a bismuth-based frit should have an optical density of more thanabout 0.1567 μm or more in order to have an effective seal width afterbeing irradiated with laser light of any one wavelength in a wavelengthrange of about 760 to about 860 nm, for example, laser light of 810 nm.The reason why the bismuth-based frit requires a higher optical densitythan the vanadium-based frit is that its material characteristics suchas the color of its mother glass are different from those of thevanadium-based frit and, accordingly, it requires a different amount ofthermal energy.

The bismuth-based frit may further include a pigment in order toincrease its optical density. The pigment added to the frit can changethe color of the entire frit. Since the bismuth-based glass is whitishdue to properties of bismuth, it is not efficient in absorbing energyprovided by the heating member. For this reason, a pigment may be addedto the bismuth-based mother glass to change the color of the frit, sothat the frit can better absorb radiant energy. When a Mn-containingpigment is added to the frit, the optical density of the frit isincreased compared with when not added. Accordingly, the increasedoptical density of the frit may increase the effective seal width of thefrit. Here, the Mn-containing pigment may be one or more materialsselected from the group consisting of MnO, MnO₂ and Mn₃O₄. For example,Mn₃O₄ added to the frit significantly increases the optical density ofthe frit, which, in turn, ensures a sufficiently large effective sealwidth.

An increase in the content of the Mn-containing pigment in thebismuth-based frit leads to an increase in the optical density of thefrit, resulting in an increase in the effective seal width of the frit.From this perspective, the content of the Mn-containing pigment in theentire frit should be 9.9% by mole or more. To prevent sintering defectsat each frit height due to a reduction in the transmittance of laserlight, the content of the Mn-containing pigment in the entire fritshould be 11.01% by mole.

In some embodiments, the addition of a pigment to the frit may inducemelanization of the frit. The melanized frit can better absorb thermalenergy. Therefore, the pigment added to the frit increases theabsorption rate of energy generated from a laser. The increasedabsorption rate of energy increases the optical density of the frit,thus increasing the effective seal width of the frit. A pigment can beadded directly to the mother glass or can be added to the frit as anadditional component, in addition to the mother glass and the filler.

The Mn-containing pigment can be added directly to the mother glass orcan be added as an additional component, in addition to the mother glassand the filler. An excessive increase in Mn content in the mother glassmay degrade unique characteristics of the mother glass. Specifically,the mother glass, which is a glass component, has a certain flow whenmelted at an appropriate temperature. However, if the content of Mn inthe mother glass exceeds a predetermined value, the flow of the motherglass changes, making it difficult to sinter the frit. Therefore, theamount of the Mn-containing pigment added directly to the mother glassmay be limited to a predetermined amount. From this perspective, one ormore materials selected from the group consisting of MnO, MnO₂ and Mn₃O₄may be added to the mother glass in an amount of 0.1 to 2% by mole basedon the total content of the frit, and other components may be added tothe mother glass as pigments separate from the mother glass.

A pigment containing one or more materials selected from the groupconsisting of MnO, MnO₂ and Mn₃O₄ may be added not only to the fritbased on the bismuth-based mother glass but also to the frit based onthe vanadium-based mother glass.

Hereinafter, a method of manufacturing a display panel according to anexample embodiment will be described. FIG. 4 is a flowchart illustratinga method of manufacturing a display panel according to an exampleembodiment.

Referring to FIGS. 1, 2 and 4, a frit composition is coated on a secondsubstrate 300 (operation S100). The frit composition may be coated noton a first substrate 400 on which light-emitting units are disposed buton the second substrate 300 which covers the light-emitting units. Insome cases, the frit composition may be coated on the first substrate400. The frit composition may be coated on the second substrate 300using, but not limited to, a screen printing method. The fritcomposition coated on the second substrate 300 may be gel-state pasteformed by adding oxide powder and an organic material to glass powder.

The coated frit composition is plasticized (operation S200). To attachthe gel-state frit paste onto the second substrate 300 as a solid-statefrit 200, the frit composition is plasticized in a workspace such as achamber. If the frit composition is a vanadium-based frit composition,the workspace may be put in a N₂ environment. Here, a flow rate of N₂ inthe workspace may be 30 to 40% by volume or less.

The plasticizing temperature may be in a range of from about 300 toabout 500° C., preferably, about 400° C. In this plasticizing process,the organic material dissipates into the air, and the gel-state pastehardens to be attached onto the second substrate 300 as the solid-statefrit 200.

The first substrate 400 is placed on the plasticized frit 200 (operationS300). The first substrate 400 having the light-emitting units on asurface thereof is placed to face the second substrate 300 having thefrit 200 attached thereto.

Finally, thermal energy is provided to the frit 200 using a heatingmember (operation S400). The heating member may be laser light of anyone wavelength in a wavelength range of about 760 to about 860 nm, forexample, laser light of 810 nm. Laser irradiation may be performed witha power of about 12.5 to about 13.0 W. After the first substrate 400 isplaced on the frit 200, laser light of 810 nm may be irradiated to adisplay panel 100. Accordingly, the frit 200 is melted and attached tothe first substrate 400, thereby bonding the first substrate 400 and thesecond substrate 300 together. Here, if the frit 200 has an opticaldensity of 0.0683/μm or greater, a sufficient large effective seal widthcan be formed as described above. Therefore, when the first substrate400 and the second substrate 300 are attached to each other by this frit200, oxygen and moisture can be prevented from getting into a pixelregion.

The present embodiments will now be described in further detail withreference to the following experimental examples. Information notprovided below can be readily inferred by those of ordinary skill in theart, and thus a description thereof will be omitted.

Experimental Example 1 Relationship Between the Optical Density and SealWidth of a Vanadium-Based Frit

Four frit samples R1 through R4 having different optical densities wereprepared by adjusting the content of vanadium in a frit. Vanadiumcontent in the frit samples R1 through R4 satisfied R1<R2<R3<R4. Asshown in FIG. 5, the vanadium content in each of the first samples R1through R4 was adjusted such that R1 had an optical density of0.0683/μm, R2 had an optical density of 0.0795/μm, R3 had an opticaldensity of 0.0892/μm and R4 had an optical density of 0.1483/μm forlaser light of 810 nm.

Each of the frit samples R1 through R4 was coated to a width of 600 μm,and laser light of 810 nm and with an energy of 12.5 W was irradiated.However, since a seal width was not formed at all in the case of R1, theenergy of the laser light was increased to 15.5 W, and then theexperiment was conducted again. The results are shown in Table 1 andFIGS. 5 and 6. In Table 1, it is determined that an effective seal widthhas been formed when a ratio of a seal width to a frit width is 0.7 orhigher.

TABLE 1 Formation of Optical density Seal width of Seal width/ effectiveseal Sample (/μm) frit (μm) frit width width R1 0.0683 369 0.615 X R20.0795 476 0.793 ◯ R3 0.0892 491 0.818 ◯ R4 0.1483 505 0.842 ◯

Referring to Table 1 and FIGS. 5 and 6, the effective seal width was notformed in the case of R1 although the energy of the laser light wassignificantly increased. On the other hand, a sufficiently largeeffective seal width was formed in the case of R2 and R4, even with anenergy of 12.5 W, and R4 had a largest seal width. A higher opticaldensity led to a greater seal width.

It can be understood from the above results that a vanadium-based fritcan have an effective seal width only when its optical density exceeds0.0683/μm.

Experimental Example 2 Relationship Between the Optical Density and SealWidth of a Bismuth-Based Frit with or without a Mn-Containing Pigment

A frit sample P1 was prepared without adding a Mn₃O₄-containing pigmentto a bismuth-based frit, and another frit sample P2 was prepared byadding the Mn₃O₄-containing pigment to the bismuth-based frit. Then,optical densities of the frit samples P1 and P2 were measured for laserlight of 810 nm. The frit samples P1 and P2 were coated to a width of600 μm, and laser light of 810 nm and with an energy of 12.5 W wasirradiated. Then, seal widths of the frit samples P1 and P2 weremeasured, and the results are shown in Table 2 and FIGS. 7 and 8.

TABLE 2 Formation of Optical density Seal width of Seal width/ effectiveseal Sample (/μm) frit (μm) frit width width P1 0.0615 0 0 X P2 0.1732467 0.778 ◯

Referring to Table 2 and FIGS. 7 and 8, the measured optical density ofthe frit sample P1 without the Mn₃O₄-containing pigment was only0.0615/μm, while the measured optical density of the frit sample P2 withthe Mn₃O₄-containing pigment was 0.1732/μm. The frit sample P2 had a farhigher optical density than the frit sample P1. Referring to Table 2 andFIG. 7, a seal width was not formed at all in the case of P1. On theother hand, the seal width of the frit sample P2 having theMn₃O₄-containing pigment was 467 μm, thus securing a sufficiently largeseal width.

It can be understood from the above results that the addition of aMn₃O₄-containing pigment to a frit increases the optical density of afrit, thus ensuring a sufficiently large effective seal width.

Experimental Example 3 Seal Width of a Bismuth-Based Frit According toMn Content in the Bismuth-Based Frit

Three frit samples D1 through D3 having different optical densities wereprepared by adjusting the content of a Mn₃O₄-containing pigment in abismuth-based frit. As shown in Table 3, the content of Mn₃O₄ in motherglass was 0.5% by mole in the case of D1, 1.0% by mole in the case ofD2, and 2.0% by mole in the case of D3. In addition to the mother glass,8 to 9% by mole of the Mn₃O₄-containing pigment was added to each of thefrit samples D1 through D3.

Each of the frit samples D1 through D3 was coated to a width of 600 μm,and laser light of 810 nm and with an energy of 12.5 W was irradiated.Then, seal widths of the frit samples D1 through D3 were measured. Theresults are shown in Table 3 and FIGS. 9 and 10.

TABLE 3 Mn content in Formation of mother glass Seal width of Sealwidth/ effective seal Sample (mol %) frit (μm) frit width width D1 0.5450 0.750 ◯ D2 1.0 478 0.797 ◯ D3 2.0 498 0.830 ◯

Referring to Table 3 and FIGS. 9 and 10, a greater content of Mn₃O₄ in afrit led to a greater seal width of the frit. In addition, an effectiveseal width was formed in all of the frit samples D1 through D3.

It can be understood from the above results that it is desirable toincrease the content of Mn₃O₄ in order to increase the effective sealwidth of a frit.

Experimental Example 4 Optical Density Range of a Bismuth-Based Frit forLaser Sealing

To find out an optical density range for laser sealing, experiments wereconducted by varying a method of adding a Mn₃O₄-containing pigment to abismuth-based frit.

A ‘Bi mother glass’ sample was prepared without adding theMn₃O₄-containing pigment to a frit, and a ‘Bi Black mother glass’ samplewas prepared by adding the Mn₃O₄-containing pigment only to motherglass. In addition, a ‘Bi Black mother glass+pigment’ sample wasprepared by adding the Mn₃O₄-containing pigment not only to the motherglass but also to the frit.

Each frit sample was irradiated with laser light of 810 nm and with anenergy of 12.5 W to see if it had an effective seal width. The resultsare shown in Table 4 and FIG. 11.

TABLE 4 Optical density Formation of effective Sample (/μm) seal widthBi mother glass 0.0162 Not formed Bi Black mother glass 0.0284 Notformed Bi mother glass + pigment 0.1004 Not formed although a seal widthfor connecting both substrates was formed Bi Black mother glass + 0.1567Formed pigment

Referring to Table 2 and FIG. 11, the optical density of the ‘Bi motherglass’ sample was close to zero. Although the ‘Bi Black mother glass’sample showed a higher optical density than the ‘Bi mother glass’sample, it did not have an effective seal width.

The ‘Bi mother glass+pigment’ sample had an optical density of0.1004/μm. At this value, the ‘Bi mother glass+pigment’ sample had aseal width for connecting both substrates, but not an effective sealwidth.

The ‘Bi Black mother glass+pigment’ sample had an optical density of0.1567/μm and thus an effective seal width.

As apparent from the above results, when the ‘Bi Black motherglass+pigment’ sample is used as a frit for a display panel, a minimumoptical density of 0.1567 μm is required to form an effective seal widthfor connecting and sealing both substrates of the display panel.

In concluding the detailed description, those skilled in the art willappreciate that many variations and modifications can be made to thepreferred embodiments without substantially departing from theprinciples of the present embodiments. Therefore, the disclosedpreferred embodiments are used in a generic and descriptive sense onlyand not for purposes of limitation.

What is claimed is:
 1. A method of manufacturing a display panel, themethod comprising: preparing a first substrate and a second substrate;coating a frit composition, which has an optical density of more thanabout 0.0683/μm for laser light of a wavelength of about 810 nm, on thesecond substrate; stacking the first substrate on the frit composition;and sintering the frit composition by irradiating the laser light of thewavelength of about 810 nm to the frit composition.
 2. The method ofclaim 1, wherein the irradiating of the laser light is performed with apower of about 12.5 to about 13.0 W.
 3. The method of claim 1, whereinthe frit composition comprises vanadium-based mother glass and furthercomprising plasticizing the frit composition at a temperature of about300 to about 500° C. and in a workspace in an atmosphere which containsabout 30 to about 40% by volume of N₂, after the coating of the fritcomposition.
 4. The method of claim 1, wherein the frit compositioncomprises bismuth-based mother glass, and, in the coating of the fritcomposition, a frit composition, which has an optical density of about0.1567/μm or greater for the laser light of the wavelength of about 810nm, is coated on the second substrate.